Left and right side heart support

ABSTRACT

A cannulation system for cardiac support uses an inner cannula disposed within an outer cannula. The outer cannula includes a fluid inlet for placement within the right atrium of a heart. The inner cannula includes a fluid inlet extending through the fluid inlet of the outer cannula and the atrial septum for placement within at least one of the left atrium and left ventricle of the heart. The cannulation system also employs a pumping assembly coupled to the inner and outer cannulas to withdraw blood from the right atrium for delivery to the pulmonary artery to provide right heart support, or to withdraw blood from at least one of the left atrium and left ventricle for delivery into the aorta to provide left heart support, or both.

RELATED APPLICATIONS

This application is a continuation of application Ser. No. 11/018,872,filed Dec. 21, 2004 now U.S. Pat. No. 7,785,246, which is a divisionalof U.S. patent application Ser. No. 09/868,973 filed Aug. 20, 2001, nowU.S. Pat. No. 6,926,662, which is a 371 of PCT/US99/30816, filed Dec.23, 1999, which claims the benefit of U.S. Provisional Application Ser.No. 60/113,771, filed Dec. 23, 1998, each of which applications andpatent we hereby incorporate herein, in their entireties and to which weclaim priority.

BACKGROUND OF THE INVENTION

I. Field of the Invention

The invention relates generally to the field circulatory support and,more specifically, to cannulas and related methods for use incardiopulmonary bypass circuits and cardiopulmonary bypass graftprocedures.

II. Discussion of the Prior Art

To perform bypass or grafting operations, many times the heart isstopped or significantly slowed by infusing chemicals (such ascardioplegia) into the patient's heart muscle or lowering thetemperature of the heart. Additionally, the contractions of thepatient's heart may be controlled utilizing other available technology,such as pacing electrodes. Prior to slowing or stopping the heart, thepatient is placed on a cardiopulmonary bypass (CPB) circuit. Blood iswithdrawn from the patient's heart, passed through a CPB circuit(generally comprising a blood pump, oxygenator, heat exchanger, and ablood filter) before being returned to the patient through a cannulawhich may be placed within the aorta. The cannulas that are placedwithin the patient generally range in size from 12 Fr. to 51 Fr., aregenerally tubular in shape, and may be reinforced with wire. Generallyspeaking, the cannula must be sufficiently small to permit insertioninto the heart with minimal damage to the tissue, though it must belarge enough to provide sufficient blood flow. In prior art systemswhere a blood pump is used to replace or assist the function of theheart, blood must be removed from the patient's vascular system, passedthrough a pump and returned to the patient's body through a secondcannula. Present bypass techniques require many feet of flexible tubingto connect the components in which the blood must flow through. Havingthe blood in contact with such a large amount of foreign materialrequires that the blood be treated with a large volume of Heparin toprevent clotting. Also, the large priming volume causes the patient'sblood to be diluted with a large amount of saline. This serves to thinthe patient's blood and lowers the oxygenation abilities, white bloodcell count and increases the blood clotting time. While this type ofbypass circuit works well, it is nonetheless complicated and requires aconsiderable amount of setup time and must be managed and constantlymonitored by a skilled technician.

Another drawback with the prior art that, if the surgeon desires tosupport both the right and left side of the heart (bi-ventricularsupport) independently without the use of an extracorporeal oxygenator,up to four cannulas need to be placed within the patient's circulatorysystem. With the addition of each cannula, further complications mayarise. Placing multiple cannulas within the surgical field can causeclutter, thereby blocking access required to perform certain surgicalprocedures. Another danger associated with bi-ventricle support circuitsis the possible formation of emboli in the patient's blood stream. Ifsufficiently high suction exists in the left atrium, air may be drawnfrom outside the heart through the insertion incision thereby forming anair emboli.

Presently there is a trend in the surgical arts toward performingbeating heart surgery. In beating heart surgery, the patient's heart isslowed but not stopped. While performing beating heart coronary arterybypass graft (CABG), the oxygenator may be eliminated from the CPBcircuit and the patient's lungs used to oxygenate the blood. Beatingheart CABG has a number of advantages over stopped heart or full CPBCABG. Specific studies have shown that patients placed on full bypassexperience neurological problems, including but not limited to: memoryloss, speech impairment, impaired coordination, systemic inflammatoryresponse, and other complications. Also, many patients are too weakand/or infirm to survive the physical stresses associated with full CPBCABG, particularly patients of advanced age.

Due to the recency of beating heart surgery, specific cannulationsystems have not been developed for use in procedures such as beatingheart CABG. The present invention addresses this void in the prior art.

SUMMARY OF THE INVENTION

The present invention relates to systems and methods for providing fullor supplemental support for the heart during cardiac surgery. Morespecifically, the present invention provides simultaneous independentsupport of both the right and left side of the heart during cardiacsurgery such as (but not necessarily limited to) beating heart CABG orstill heart CABG.

One aspect of the invention provides a cannulation system for cardiacsupport. The system includes an inner cannula disposed within an outercannula. The outer cannula includes a fluid inlet for placement withinthe right atrium of a heart. The inner cannula includes a fluid inletextending through the fluid inlet of the outer cannula and the atrialseptum for placement within at least one of the left atrium and leftventricle of the heart. The cannulation system also includes a pumpingassembly coupled to the inner and outer cannulas to withdraw blood fromthe right atrium for delivery to the pulmonary artery to provide rightheart support, or to withdraw blood from at least one of the left atriumand left ventricle for delivery into the aorta to provide left heartsupport, or both.

In a preferred embodiment, a cannula assembly and a pumping systemcooperate to provide left and/or right heart support during cardiacsurgery. The cannula assembly includes an inner cannula disposedgenerally coaxially within an outer cannula. To establish a bypasscircuit with the present invention, the coaxial cannula assembly isintroduced into the patient's heart through a single incision in theright atrium. The distal tip of the outer cannula is placed within thepatient's right atrium. The inner cannula extends outwardly through anaperture formed in the distal end of the outer cannula and is passedthrough the atrial septum such that the distal end of the inner cannulais disposed within the patient's left atrium, or alternatively, withinthe patient's left ventricle. The pumping system includes a first bloodpump connected to the proximal end of the outer cannula, and a secondblood pump connected to the proximal end of the inner cannula. The firstblood pump withdraws blood from the right atrium, which blood passes tothe first blood pump through the annular flow path formed between theexterior surface of the inner cannula and the interior surface of theouter cannula. The outflow of the first blood pump is connected to anoutflow cannula placed within the pulmonary artery, thereby providingright heart support. The second blood pump withdraws blood from the leftatrium and/or left ventricle, which blood passes to the second bloodpump through the flow path defined within the lumen of the innercannula. The outflow of the second blood pump is connected to an outflowcannula placed within the aorta or any other major artery, therebyproviding left heart support.

The cannula assembly of the present invention may be inserted eitherthrough an open chest cavity, such as when the patient's sternum isspread, or may be inserted during minimally invasive procedures wherethe cannula is placed within the patient's heart through access portalsin the patient's chest. The associated methods of the present inventionmay also be used with a coaxial cannula, which consists of an inner andan outer cannula, that may be inserted through the patient's peripheralvasculature such as the jugular vein or femoral vein.

The cannulation system of the present invention provides independentdrainage of the patient's left and right heart while minimizing thenumber of devices necessary to provide a bypass circuit. In a typicalCPB circuit, many feet of flexible tubing are utilized to connect thebypass cannulas to the external support circuit, which typicallyconsists of a blood pump, oxygenator and other components. As thepatient's blood flows through the tubing, the blood is activated due tothe contact with foreign materials, thereby activating the patient'simmune system. Thus, after completion of the surgical procedure, thepatient's immune system is further weakened due to the materialsutilized during the procedure. The cannulation system of the presentinvention eliminates the oxygenator, blood filter, and the many feet oftubing typically found in a traditional CPB circuit. Eliminating theoxygenator and blood filter from the bypass circuit reduces hemolysis byminimizing the extent to which blood contacts foreign surfaces. Reducingthe tubing serves to lower the priming volume of the bypass circuit,which in turn lessens the amount of saline introduced into the bloodduring priming operations. Minimizing the amount of saline added to theblood reduces the possibility that the patient will require a bloodtransfusion.

The cannulation system of the present invention is furthermore able toprovide independent drainage of the patient's left and/or right heartthrough a single incision. In so doing, the cannulation system of thepresent invention reduces the possibility of air emboli forming within(or being introduced into) the patient's blood stream. In prior artcannulation arrangements, an incision must be made within the leftatrium to receive a cannula coupled to a pump for withdrawing bloodtherefrom. If sufficient negative pressure develops within the leftatrium, air may be drawn through the incision in the left atrium andform air emboli within the patient's blood stream. The cannulationsystem of the present invention positions the inner cannula within theleft atrium by passing through the atrial septum, thereby eliminatingthe need for an incision in the outer wall of the left atrium.Therefore, to the extent sufficiently high negative pressures develop inthe left atrium, the cannulation system of the present invention ensuresthat only non-oxygenated blood will be drawn through the atrial septumfrom the right atrium. In so doing, the present invention eliminates thepossibility of air emboli forming in the patient's blood stream.

Utilizing the cannulation system of the present apparatus, a flow rateup to 6 liters per minute may be obtained with 100 mmHg outflow pressureand a rotational speed approximately between 2,000 and 50,000 rpm.

The coaxial cannula of the present invention may further include meansfor monitoring pressures within the patient's circulatory system. Thecannula of the present invention can include devices such as pressuretransducers and lumens disposed within the wall of the cannula. Byincorporating sensing devices within the cannula of the presentinvention, further incisions and devices may be eliminated from thebypass circuit, thereby simplifying the circuit and reducing the overallcost of the procedure.

In an alternative embodiment, the cannula of the present invention mayfurther contain a supplemental perfusion/drainage line for infusingcardioplegia into the heart or as a vent line for the heart.

In another embodiment of the present invention, any number of sensingdevices may be employed to determine the location of the distal tip ofthe coaxial cannula within the patient's heart, including but notlimited to a Doppler sensor, an ultrasound sensor, piezoelectric orsilicone pressure sensor, and/or an oxygen saturation sensor.

In a still further embodiment of the present invention, thebiventricular support system may further comprise a blood filter, abubble trap, a means for oxygenating the patient's blood and a means forsalvaging and re-infusing blood during the surgical procedure.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in greater detail with reference tothe preferred embodiments illustrated in the accompanying drawings, inwhich like elements bear like reference numerals, and wherein:

FIG. 1 is a schematic view of a cannulation system of the presentinvention in use with a human heart for providing right and/or leftheart support during cardiac surgery;

FIG. 2 is a side view of the cannulation system of FIG. 1, furtherillustrating the cannula assembly as including an inner cannula disposedwithin (and extending from) an outer cannula;

FIG. 3 is a side view of the inner cannula of FIGS. 1 and 2 equippedwith a dilator assembly for facilitating passage of the inner cannulathrough the atrial septum according to the present invention;

FIG. 4 is a side view of an alternate embodiment of the cannula assemblyof the present invention wherein the outer cannula is equipped with adilator tip to facilitate the introduction of the inner cannula into theleft atrium;

FIG. 5 is a side view of an alternate embodiment of the cannula assemblyof the present invention wherein the outer cannula is equipped with aninflatable cuff assembly;

FIG. 6 is a side view of the cannula assembly of FIG. 5 with theinflatable cuff assembly deployed about either side of the atrialseptum;

FIG. 7 is a side view of an alternate embodiment of the cannula assemblyof the present invention wherein the outer cannula is equipped with abuckling cuff assembly;

FIG. 8 is a side view of the cannula assembly of FIG. 7 with thebuckling cuff assembly deployed about either side of the atrial septum;

FIG. 9 is a side view of an alternate embodiment of the inner cannula ofthe present invention;

FIG. 10 is a cross sectional view of the inner cannula taken throughlines 10-10 of FIG. 9;

FIG. 11 is a side view of an alternate embodiment of the outer cannulaof the present invention;

FIG. 12 is a cross sectional view of the inner cannula taken throughlines 12-12 of FIG. 11;

FIG. 13 is a schematic view of an alternate embodiment of the presentinvention wherein the cannulation system includes a supplementalperfusion conduit for delivering oxygen-rich blood from the left atriumto a target vessel (T) on the heart;

FIG. 14 is a schematic view of another cannulation system of the presentinvention in use with a human heart for providing right and/or leftheart support during cardiac surgery;

FIG. 15 is a side view of the cannulation system of FIG. 14, furtherillustrating the cannula assembly as including a pair of inner cannulasdisposed within (and extending from) an outer cannula;

FIG. 16 is an alternate embodiment of the cannulation system shown inFIGS. 14 and 15, wherein an inflatable balloon is provided on the distalend of an outflow cannula 180 for selectively occluding the aorta;

FIG. 17 is a cross sectional view of the outflow cannula 180 takenthrough lines 17-17 of FIG. 16;

FIG. 18 is a partial sectional side view illustrating an alternativeembodiment of forming the balloon on the distal tip of outflow cannula180; and

FIG. 19 is a schematic view of an alternate embodiment of the presentinvention wherein the cannulation system includes a system for infusingchemicals into the patient's heart or, alternatively, for withdrawingblood from the left ventricle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention involves a method and apparatus for providing fullor supplemental support for the heart during cardiac surgery. Referringto FIG. 1, a cannulation system 5 according to one embodiment of thepresent invention is provided comprising a coaxial cannula assembly 10having an outer cannula 14 extending into the right atrium of apatient's heart, and an inner cannula 12 disposed generally coaxiallywithin an outer cannula 14 and extending through the atrial septum intothe left atrium. As will be explained in greater detail below, thecoaxial cannula assembly 10 has an inner flow path defined by the lumenwithin the inner cannula 12, and an outer flow path defined by theannular channel extending between the interior surface of the outercannula 14 and the exterior surface of the inner cannula 12. The innercannula 12 is communicatively coupled to a blood pump 75 such thatoxygen-rich blood from the left atrium may be withdrawn via the innerflow path and rerouted into the aorta via an outflow cannula 80. Theouter cannula 14 is communicatively coupled to a blood pump 76 such thatoxygen-depleted blood from the right atrium may be withdrawn via theouter flow path and rerouted into the pulmonary artery via an outflowcannula 82. In this fashion, the cannulation system of the presentinvention is capable of providing full or partial support to both theright and left sides of the heart during heart surgery.

Referring to FIG. 2, the outer cannula 14 includes a generallycylindrical hollow body 8 extending between a proximal end 16 and adistal end 17, and a fluid inlet port 20 coupled to the distal end 17.The fluid inlet port 20 includes an aperture 15 at its distal end andplurality of apertures 21. The aperture 15 of fluid inlet port 20permits the inner cannula 12 to extend past the distal end of the outercannula 14 for insertion through the atrial septum and placement withinthe left side of the heart. The apertures 21 of fluid inlet port 20permit the inflow of blood into the outer flow path formed between theexterior of the inner cannula 12 and the interior surface of the outercannula 16 when the inner cannula 12 is disposed within the outercannula 14. The inner cannula 12 includes a hollow body portion 9extending between a proximal tip 11 and a distal tip 22. The distal tip22 and proximal tip 11 each contain an aperture to permit fluid flowthrough the lumen extending therebetween. The proximal tip 11 of innercannula 12 is coupled to the blood pump 75. The distal tip 22 of innercannula 12 is adapted to be passed through the outer cannula 14, throughthe patient's atrial septum, and into position within the left atriumand/or left ventricle. A plurality of supplemental fluid inlet apertures23 may be provided near the distal tip 22 of the inner cannula 12 tofacilitate the inflow of blood from the left side of the heart into tothe pump 75.

The cannula assembly 10 of the present invention may be formed ofmaterials ranging from rigid to flexible. These materials may besilicone rubber or a similar material, although preferably the cannulaassembly 10 will be constructed of a semi-rigid transparent materialsuch as polyurethane or polyvinyl chloride. The inner and outer cannulas12,14 of the present invention may contain a spiraling wire disposedwithin the cannula wall to reinforce the central portions thereof.Providing reinforcement in this manner facilitates easy handling andprevents the inner and outer cannulas 12, 14 from collapsing or beingpinched shut, which may otherwise close off the flow of fluid to or fromthe patient. Other ways of reinforcing the tubular body of a cannula areknown in the art and will adapt equally well to the present invention.In addition, no reinforcement may be needed if the tube material issufficiently strong or if sufficient positive pressure is present withineach cannula 12, 14. The distal tips of each cannula 12,14 arepreferably designed so that they do not cause damage to the surroundingtissue when inserted into the patient. The cannulas 12, 14 may be formedeither by extrusion, or a layering process whereby successive layers ofmaterials are deposited on a mandrel until a desired wall thickness isachieved. Additionally, as will be discussed below, one or more lumensmay be formed within the wall of the cannulas 12, 14 during constructionto, for example, house sensing devices such as blood pressure sensors,oxygenation sensors, etc.

Referring to FIG. 3, the step of passing the inner cannula 12 throughthe atrial septum may be accomplished through the use of a dilatorassembly 30. Dilator assembly 30 includes a dilator 31, a needle 35disposed within a lumen formed within the dilator 31, and a guide wire37 disposed within a lumen formed within the needle 35. The dilator 31has a distal tip 32 and a proximal tip 33 and a lumen extendingtherebetween. The dilator 31 is disposed through the main lumen of innercannula 12. Distal tip 32 of dilator 30 protrudes beyond distal tip 22of inner cannula 12. Distal tip 36 of needle 35 protrudes beyond distaltip 32 of dilator 31. The distal tips 32, 36, 38 of each component ofthe dilator assembly 30 are designed with sufficient rigidity and/orsharpness such that, alone or in combination, they provide the abilityto pierce the atrial septum to facilitate passage of the inner cannula12 therethrough. A hemostasis valve 39 may be provided at the proximalend 11 of inner cannula 12 in an effort to minimize or prevent bloodflow out of (or air flow into) the heart during the process of passingthe dilator assembly 30 through the inner cannula 12. It is to readilyunderstood that the dilator assembly 30 is well known in the art and setforth by way of example only. Any number of additional commerciallyavailable dilator devices or assemblies can be employed to facilitatepassing the distal tip 22 of the inner cannula 12 through the atrialseptum for placement in the left side of the heart.

The method of inserting the cannula assembly 10 into the patient usingthe dilator assembly 30 will now be described with reference to FIGS. 1and 3. The outer cannula 14 is first inserted into the patient's rightatrium through an incision. After inserting outer cannula 14 into theright atrium, the inner cannula 12 is prepared for insertion byintroducing the dilator assembly 30 and guidewire 37 through the mainlumen of the inner cannula 12. This forms the inner cannula assemblyshown in FIG. 3. The inner cannula assembly is then advanced throughhemostasis valve 92, distally through the main lumen of the outercannula 14, and out the exit aperture formed in the fluid inlet port 20.The inner cannula assembly is then advanced through the right atriumuntil the needle 35 pierces the atrial septum. In this fashion, a usermay then advance the entire dilator assembly 30 through the patient'satrial septum. Dilator 31 expands the opening in the atrial septum to asufficient diameter to allow the inner cannula 12 to pass throughtherethrough. After placing the distal tip 22 of the inner cannula 12within the left atrium, the dilator assembly 30 may be withdrawn fromthe main lumen of inner cannula 12.

As shown in FIGS. 1 and 2, the inner cannula 12 and outer cannula 14 arecoupled to the pumps 75, 76 through the use of a Y-connector 90. TheY-connector 90 is a generally cylindrical tubular member having ahemostasis valve 92 at its proximal end and coupled to the outer cannula14 at its distal end. The Y-connector 90 has a main lumen through whichthe proximal end 11 of the inner cannula 12 extends for passage throughthe hemostasis valve 92 and connection to the pump 75. Under thedirection of the pump 75, oxygen-rich blood from the left side of theheart may be withdrawn through the inner flow path (within the innercannula 12), passed through the hemostasis valve 92 to the pump 75, andpassed through the outflow cannula 80 for deposit into the aorta. TheY-connector 90 also includes a secondary lumen extending within a port93 extending angularly from the main body of the Y-connector 90. Theport 93 is connected to the pump 76 through the use of a coupler 91 andconduit 94. Under the direction of the pump 76, oxygen-depleted bloodfrom the right atrium may be withdrawn through the outer flow path(between the outer cannula 14 and inner cannula 12), passed through theport 93 to pump 76, and passed through the outflow cannula 82 fordelivery into the pulmonary artery.

It is to readily understood that the Y-connector 90 is well known in theart and set forth by way of example only. Any number of additionalcommercially available coupling devices or assemblies can be employedwithout departing from the scope of the present invention. Y-connector90 is preferably constructed of a clear rigid material, preferably apolycarbonate material, although Y-connector 90 may be constructed ofany other clear or opaque rigid or semi-rigid biocompatible material. Itis to be understood that the individual components shown associated withthe Y-connector 90 (i.e. coupler 91 and hemostasis valve 92) are wellknown in the art and may comprise any number of similar commerciallyavailable devices without departing from the scope of the invention. Forexample, coupler 91 may comprise any well known and/or commerciallyavailable connecting barb or quick disconnect coupler. The hemostasis 92may also comprise the proprietary hemostasis valves disclosed inco-pending and commonly assigned U.S. patent application Ser. No.09/163,103 (filed Sep. 29, 1998 and entitled “Hemostasis Valve withMembranes Having Offset Apertures”) and/or U.S. patent application Ser.No. 09/163,102 (filed Sep. 30, 1998 and entitled “Hemostasis Valve WithSelf-Sealing Flap”), both of which are hereby expressly incorporatedherein by reference in their entirety. Outflow cannulas 80, 82 maycomprise any number of commercially available conduits. As will be shownand described in greater detail below, outflow cannulas 80, 82 may alsobe equipped with at least one balloon disposed radially about the outersurface of the each outflow cannula 80, 82. In this fashion, onceinserted within the patient's aorta and pulmonary artery, the balloonsmay be inflated to occlude the aorta and pulmonary artery to preventblood from flowing retrograde into the patient's heart.

The pumps 75, 76 may comprise any number of pumping arrangements capableof providing full or partial support to the right and/or left heartduring cardiac surgery. Such pumping arrangements can include, but arenot necessarily limited to, any number of centrifugal pumps, axialpumps, and/or roller pumps that are well known in the art andcommercially available, such as the 3M Sarns pump. Another pumpingarrangement suited for use with the present invention is disclosed inco-pending and commonly assigned U.S. patent application Ser. No.09/166,135 (filed Sep. 30, 1998 and entitled “Blood Pump With SterileMotor Casing”), the contents of which are hereby expressly incorporatedherein by reference. The cannulation system of the present apparatus iscapable of providing right and left heart support at flow rates up to 6liters per minute with 100 mmHg outflow pressure and a rotational pumpspeed of approximately between 2,000 and 50,000 rpm.

FIG. 4 illustrates an alternate embodiment of the cannula assembly 10 ofthe present invention, wherein the outer cannula 14 is provided with aguiding dilator 24 extending distally from the fluid inlet port 20. Theguiding dilator 24 comprises a tubular member having an interiorlydisposed lumen and a distal tip 25 having an aperture through which theinner cannula 12 may be passed for insertion through the atrial septumand placement within the left side of the heart. Guiding dilator 24 ispreferably formed of a sufficiently rigid material such as urethane,silicone, or polyvinyl chloride. Guiding dilator 24 is formed such thatupon inserting the outer cannula 14 within the right atrium, the distaltip 25 of guiding dilator 24 is advanced through the atrium septum anddisposed within the left atrium. Distal tip 25 of guiding dilator 24 isadapted to puncture and expand the atrial septum. Additionally, guidingdilator 24 is further adapted to guide the inner cannula 12, so that thedistal tip 22 of inner cannula 12 may be easily placed within the leftatrium or left ventricle. In this regard, guiding dilator 24 may containa curved portion or be formed substantially straight as illustrated inFIG. 4. The outer cannula 14 is shown having the fluid inlet port 20 andguiding dilator 24 formed as a unitary article. Outer cannula 14 may beconstructed in this fashion by carrying out the following steps: (1)selecting an appropriate sized mandrel; (2) pre-heating the mandrel to aselected temperature between about 100 and 300 degrees Celsius; (3)applying a layer of liquid material to the mandrel; (4) curing the firstlayer by applying heat; (5) disposing reinforcing wire about mandrel;(6) applying a second layer of material; and (7) curing the second layerof material by application of heat. It will be readily appreciated that,while shown as part of a unitary article in FIG. 4, it is within thescope of the present invention to provide the guiding dilator 24 andfluid inlet port 20 as separate elements coupled to the outer cannula14.

FIG. 5 illustrates an alternate embodiment of the cannula assembly 10described above, wherein outer cannula 14 is further equipped with aninflatable cuff assembly 26. The inflatable cuff assembly 26 includes apair of inflation members 27 (such as balloons) radially disposed aboutthe guiding dilator 24. The inflation members 27 are coupled to a fluidsource (not shown) and adapted to receive or sandwich the patient'stissue therebetween when inflated. FIG. 6 illustrates the inflatablecuff assembly 26 in use, with the individual inflation members 27inflated and disposed on either side of the atrial septum. To accomplishthis, the cannula assembly 10 is first introduced into the right atriumwith the inflation members 27 in a fully deflated or low profile state.The outer cannula 14 is advanced within the right atrium until thedistal tip 25 of the guiding dilator 24 pierces the atrial septum,allowing the placement of the inner cannula 12 within the left side ofthe heart. The guiding dilator 24 is preferably positioned such that theinflation members 27 are disposed on either side of the atrial septum.The inflation members 27 may thereafter be selectively inflated throughthe use of a fluid source (not shown) to secure a portion of the atrialseptum therebetween. The inflatable cuff assembly 26 thereby provides aseal between the right atrium and the left atrium. Further still, theinflatable cuff assembly 26 serves to position and retain the cannulaassembly 10 within the heart.

FIG. 7 illustrates an alternate embodiment of the cannula assembly 10described above, wherein outer cannula 14 is further equipped with abucking cuff assembly 56. The buckling cuff assembly 56 includes alength of fabric capable of having its ends or portions selectivelydrawn together to create a pair of cuff members 57 radially disposedabout the guiding dilator 24. The step of drawing the ends or portionsof the fabric together may be accomplished through the use of wires 58disposed within lumens (not shown) formed in the wall of the outercannula 14. It also may be possible to provide a slidable member (notshown) between the distal tip 25 of the guiding dilator 24 and thedistal end of the fabric such that the slidable member can be drawnproximally towards the fluid inlet 20 to create the bucking cuffs 57. Ineither case, FIG. 8 illustrates the buckling cuff assembly 56 in use,with the individual cuff members 57 disposed on either side of theatrial septum. To accomplish this, the cannula assembly 10 is firstintroduced into the right atrium with the fabric extended in a lowprofile state such that the cuff members 57 are not formed. The outercannula 14 is advanced within the right atrium until the distal tip 25of the guiding dilator 24 pierces the atrial septum, allowing theplacement of the inner cannula 12 within the left side of the heart. Theguiding dilator 24 is preferably positioned such that the fabric extendson either side of the atrial septum. The cuff members 57 may thereafterbe selectively formed by drawing the wires 58 to secure a portion of theatrial septum therebetween. The buckling cuff assembly 56 therebyprovides a seal between the right atrium and the left atrium. Thebuckling cuff assembly 56 also serves to position and retain the cannulaassembly 10 within the heart. As used herein, the term “fabric” refersto any structure produced by interlacing fibers. Such fibers include anythreadlike material adapted for spinning or weaving. The fibers may beinorganic or organic. The fibers may also be constructed from any numberof filaments or have a mono-filament construction. Suitable materialsfor the fabric can include polyester, polyethylene, nylon, polyefin,polypropylene, PTFE and polyurethane and silicone.

FIGS. 9 and 10 illustrate an alternate embodiment of the inner cannula12 equipped with a variety of additional features according to thepresent invention. In addition to the main lumen 15, the inner cannula12 may be further equipped with one or more lumens 60 disposed withinthe side wall 17. Lumens 60 may be used for pressure measurements,injecting or withdrawing fluid, or for inflating balloon 27. Lumens 60may also be used to receive a light guide, such as a fiber optic cable42, for the purpose of projecting light from the distal end of the innercannula 12. The illuminating tip of fiber optic cable 42 provides theuser with direct or indirect visual reference that aids in placement ofinner cannula 12. The lumens 60 of the inner cannula 12 are alsosuitable for receiving at least one pressure transducer 43. Pressuretransducer 43 may be placed sufficiently close to the inner wall ofinner cannula 12, thereby allowing the user to measure pressure and flowrate within inner cannula 12. Transducer 43 may be placed sufficientlyclose to the outer surface of inner cannula 12 to measure pressure andflow rate through outer cannula 14.

The inner cannula 12 may also be equipped with features for determiningor tracking the location of the inner cannula 12 within the heart. Forexample, inner cannula 12 may further contain sensors (not shown) fordetermining oxygenation content within the patient's blood, such assaturated venous oxygen sensors. As distal tip 22 is advanced throughthe atrial septum into the left atrium, the oxygen content of the bloodwill increase, thereby signaling to the user that distal tip 22 isplaced within the left atrium. Therefore, by measuring the oxygencontent, the position of the distal tip 22 of cannula 12 may be readilydetermined. The inner cannula 12 may also be equipped with an ultrasoundsensor disposed about or within the distal tip 22 of the inner cannula12. When inserting inner cannula 12 into the heart, the user maydetermine placement of the distal tip 22 by monitoring the ultrasoundsensor. As indicated by the sensor, areas of high flow will cause analarm to sound, thereby alerting the user that the distal tip 22 may beimproperly placed within a vessel or chamber of the heart. An example ofsuch a use would be when advancing the inner cannula 12 toward theatrial septum, the ultrasound sensor will sound if the distal tip 22 isseated against the aorta instead of the atrial septum. In this fashion,a user will be provided a warning that a correction in alignment must bemade. The ultrasound sensor may also be used to provide pressuremeasurements from the distal tip 22 of inner cannula 12 during insertionand after insertion. These pressure measurements may be utilized todetermine the orientation of distal tip 22 with respect to the atrialseptum.

FIGS. 11 and 12 illustrate an alternate embodiment of the outer cannula14 equipped with a variety of additional features according to thepresent invention. In addition to the main lumen 13, the outer cannula14 may be further equipped with one or more lumens 80 disposed withinthe side wall 18. Lumens 80 may be used for pressure measurements,injecting or withdrawing fluid, or for inflating a balloon (not shown)disposed about the outer surface of cannula 14. Lumens 80 may also beused to receive a light guide, such as a fiber optic cable 45, for thepurpose of projecting light from the distal end of the outer cannula 14.The illuminating tip of fiber optic cable 45 provides the user withdirect or indirect visual reference that aids in placement of outercannula 14. The lumens 80 of the outer cannula 14 are also suitable forreceiving at least one pressure transducer 47. Pressure transducer 47may be placed sufficiently close to the inner wall of the main lumen 13of outer cannula 14, thereby allowing the user to measure pressure andflow rate within outer cannula 14. The pressure transducer 47 may alsobe placed sufficiently close to the outer surface of outer cannula 14 tomeasure pressure and flow rate around outer cannula 14.

The outer cannula 14 may also be equipped with features for determiningor tracking the location of the outer cannula 14 within the heart. Forexample, the outer cannula 14 may be equipped with an ultrasound sensordisposed about or within the distal tip of the outer cannula 14. Wheninserting outer cannula 14 into the heart, the user may determineplacement of the distal tip or fluid port 20 by monitoring theultrasound sensor. High flow rate measurements will cause an alarm tosound. As such, a user may be alerted by the alarm when high flow ratesare measured due to the distal tip or fluid port 20 being improperlyplaced within a vessel or chamber of the heart. The ultrasound sensormay also be used to provide pressure measurements from the distal tip orfluid port 20 of the outer cannula 14 during insertion and afterinsertion. These pressure measurements may be utilized to determine theorientation of the distal tip or fluid port 20 of the outer cannula 14with respect to the atrial septum.

FIG. 13 illustrates an alternate embodiment of the cannulation system 5of the present invention, wherein a supplemental perfusion conduit 85 isprovided for perfusing a target vessel or artery (T) of the patientduring surgical procedures. When performing an anastomosis, the surgeontypically occludes the target vessel (T) proximal to the arteriotomy(A). However, in so doing, this effectively cuts off the blood supply tothe heart tissue downstream or distal to the occlusion (O) such thatthis tissue may not receive an adequate amount of oxygenated blood. Aswill be appreciated, this may cause damage to the tissue. In theembodiment shown, the supplemental perfusion conduit 85 is coupled tothe outflow cannula 82 such that oxygen rich blood may be diverted intothe target vessel (T) to perfuse the vessels distal to the arteriotomy(A). The supplemental perfusion conduit 85 may be provided with astopcock 71 and flow regulator 72 disposed in-line to allow greatercontrol over fluid flow rate through conduit 85 and/or to allow infusionof chemicals into the patient's circulatory system. Although not shown,it will be apparent to those skilled in the art that the supplementalperfusion arrangement discussed above may also be coupled to the outflowcannula 82 such that blood from the right atrium may be diverted forperfusing a target vessel or artery (T) of the patient during surgicalprocedures, albeit with blood having a lower oxygen content.

FIG. 14 illustrates a cannulation system 105 according to an alternateembodiment of the present invention. The cannulation system 105comprises a cannula assembly 100 having a variety of pumps and conduitscoupled thereto for providing full or partial support to both the rightand left sides of the heart during heart surgery. The cannula assembly100 includes an outer cannula 114, an inner cannula 112, and an innercannula 113. As will be explained in greater detail below, the innercannula 112 cooperates with a pump 175 and an outflow cannula 180 towithdraw oxygen-rich blood from the left atrium for deposit in the aortato thereby provide left heart support. The inner cannula 113 and outercannula 114 cooperate with a pump 176 to withdraw oxygen-depleted bloodfrom the right atrium for deposit in the pulmonary artery to therebyprovide right heart support.

With combined reference to FIGS. 15 and 16, the outer cannula 114includes a main body portion 108 and a curved guiding portion 107extending therefrom. The main body portion 108 includes a fluid inletregion 120 disposed within the right atrium having a plurality ofapertures 121. The guiding portion 107 is a hollow and curved conduitextending from the fluid inlet region 120 of the main body portion 108into the right ventricle. As can best be seen in FIG. 15, the guidingportion 107 has a curved or bent configuration that, when disposedwithin the right ventricle, directs the inner cannula 113 into thepulmonary artery. The inner cannula 112 has a distal end 122 extendingthrough the atrial septum into the left atrium, a proximal end 111coupled to the pump 175, and a mid-portion 109 extending therebetweenwhich passes through the lumen of the outer cannula 114. Under thedirection of the pump 175, oxygen-rich blood is withdrawn from the leftatrium and transported through the inner cannula 112, the pump 175, andthen through an outflow cannula 180 for deposit into the aorta. Theinner cannula 113 has a distal end 126 extending into the pulmonaryartery, a proximal end 128 coupled to the pump 175, and a mid-portion129 extending therebetween which passes through the main lumen andcurved guiding conduit 107 of the outer cannula 114. Under the directionof the pump 176, oxygen-depleted blood from the right atrium iswithdrawn through the fluid inlet region 120 and transported through theouter cannula 114 (along the exterior surfaces of the inner cannulas112, 113), the pump 176, and then through the inner cannula 113 fordeposit in the pulmonary artery. A plurality of supplemental fluid inletapertures 123 may be provided near the distal tip 122 of the innercannula 112 to facilitate the inflow of blood from the left side of theheart into the pump 175. In similar fashion, a plurality of supplementalfluid inlet apertures 131 may be provided near the distal tip 126 of theinner cannula 113 to facilitate the outflow of blood into the right sideof the heart from the pump 176.

A pair of Y-connectors 190 a, 190 b are provided, one (190 a) coupled tothe proximal end 116 of the outer cannula 114, and the other (190 b)coupled to the port 193 of Y-connector 190 a. The pump 176 may becoupled to Y-connector 190 a via any number of conduits, such as tubularmember 133. The proximal end 128 of inner cannula 113 is coupled to thepump 176. The mid-portion 129 of inner cannula 113 extends through thehemostasis valve 192 and main lumen of Y-connector 190 b before passingthrough the lumens of Y-connector 190 a, the main body portion 108, andthe curved guiding portion 107 for passage into the pulmonary artery.The proximal end 111 of the inner cannula 112 is coupled to the inflowof pump 175. The mid-portion 109 of inner cannula 112 extends throughthe hemostasis valve 192 and lumens of Y-connector 190 b before passingthrough the lumens of Y-connector 190 a and the main body portion 108for passage through the atrial septum and into the left atrium. Althoughnot shown, it is to be readily understood that the cannulation system105 can be equipped with a supplemental perfusion system as shown anddescribed above with reference to FIG. 13, which perfusion system can beused with the coronary sinus for retrograde perfusion of coronaries.

FIGS. 16 and 17 illustrate an alternative embodiment of the cannulationsystem 105 of the present invention, wherein the outflow cannula 180 isprovided with a balloon 127 disposed about the outer surface adjacent todistal tip 181 for the purpose of selectively occluding the aorta. Theballoon 127 is coupled to a fluid source 151 capable of selectivelyinflating and deflating the balloon 127. The fluid source 151 isprovided with a tube 150 which extends through a lumen 160 formed withinthe outflow cannula 180 for connection to the interior of the balloon127. In one exemplary embodiment, the fluid source 151 may comprise asyringe which, when filled with saline or carbon dioxide, may beutilized to inflate or deflate balloon 127. Skilled artisans willappreciate that this is essentially the same as required for inflatingand deflating the inflation members 27 discussed above with reference toFIGS. 9 and 10. The balloon 127 may be constructed from a resilient andflexible material, such as latex, silicone or urethane, sealed at itsperiphery against wall 182 of cannula 180. The sealing can be effectedusing heat bonding and/or any suitable adhesive. While deflated, theballoon 127 lies in a flush or low profile fashion against the surfaceof cannula 180. When inflated, the balloon 127 increases in size andsurface area to occlude the patient's aorta.

FIG. 18 illustrates an alternate construction for balloon 127, whereinthe outflow cannula 180 has a layered construction with an inner wallportion 146 folded outward and sealed against an outer wall portion 144to thereby form a fluid-tight continuous pocket comprising balloon 127.Portions 144 and 146 may be different materials, and they may be sealedtogether, by way of example, using heat bonding and/or adhesive atjunction 148. As shown, supply tube 165 feeds into this pocket bypassing between wall portions 144 and 146. However, this is not a strictrequirement such that other ways of supplying balloon 127 with inflatingmaterial may be employed without departing from the scope of the presentinvention.

FIG. 19 illustrates an alternate embodiment of the cannulation system105 of the present invention, wherein a system 170 is provided forinfusing chemical such as cardioplegia into the patient's heart or,alternatively, for withdrawing blood from the left ventricle. The system170 includes a tube 153 which extend from a valve fitting 154, passesthrough a lumen formed within the outflow cannula 180 (such as lumen 160of FIG. 17), and exits cannula 180 adjacent to balloon 127 for passageinto the aorta. The valve fitting 154 may comprise a multi-positionstopcock, which allows the user to select whether to employ the system170 for infusing chemicals into, or withdrawing blood from, the aorta.When the system 170 is utilized for drainage, a second tube 157 ispreferably provided coupling the valve fitting 154 to the inflow side ofpump 175. The valve fitting 154 may then be employed to establish fluidcommunication between the pump 175 and the tube 153 such that blood maybe withdrawn from the aorta under the direction of the pump 175. Whenutilized for chemical infusion, the valve fitting 154 may be coupled toa source of chemicals (such as a syringe having cardioplegia disposedtherein) and employed to deliver the chemicals into the aorta.

Although not shown, any number of additional devices may be disposedwithin either or both bypass circuits. For example, a blood filterand/or heat exchanger may be disposed within the left heart bypasscircuit by positioning these devices between the pump 75 and the aorta.Similarly, a blood filter and/or heat exchanger may be disposed withinthe right heart bypass circuit by positioning these devices between thepump 76 and the pulmonary artery.

The above are exemplary modes of carrying out the invention and are notintended to be limiting. It will be apparent to those skilled in the artthat modifications thereto can be made without departing from the spritand scope of the invention. Though the device and methods of the presentinvention are illustrated as being inserted directly into the heart,this does not preclude other methods of insertion, such as accessthrough the femoral artery/vein and/or jugular vein/artery. It is alsoto be understood that, although the inner cannulas 12, 112 are shownwith their distal tips 22, 122 extending into the left atrium, it iscontemplated as part of the present invention that the inner cannula 12,112 can be extended further into the left heart such that distal tips22, 122 are disposed within the left atrium. It should also berecognized that, when utilizing the present invention for supporting theheart, the patient's heart may be stopped or significantly slowed byinfusing drugs into the heart. Although described within the applicationas being of a coaxial embodiment, different geometrical embodiments arealso contemplated. One such embodiment may be a dual lumen cannulahaving parallel cannulas.

We claim:
 1. A cannulation system for cardiac support comprising: aninflow cannula including a fluid inlet sized and configured to extendthrough an atrial septum for accessing at least one of a left atrium anda left ventricle of a heart and a lumen extending proximally of thefluid inlet; said inflow cannula being configured to couple to a pump towithdraw blood from the left side of the heart through the lumen; anoutflow cannula configured to couple to the pump and adapted to extendinto the arterial system for delivering the withdrawn blood into thearterial system to provide left heart support; and at least one radiallyextending member adjacent to the fluid inlet and configured for securingthe cannula system in position through the atrial septum.
 2. Thecannulation system of claim 1, further comprising a dilator memberdisposed proximally of the fluid inlet adapted to facilitate passing thefluid inlet of the cannula through the atrial septum for positioningwithin the left side of the heart, wherein the radially extending memberis coupled with the dilator member and comprises an inflatable cuffassembly adapted for securing the dilator member in position through theatrial septum.
 3. The cannulation system of claim 2, wherein theinflatable cuff assembly includes a first inflation member and a secondinflation member which, in use, are adapted to be deployed on eitherside of the atrial septum.
 4. The cannulation system of claim 3, whereinthe inflation members are selectively deployable through the use of afluid source coupled to the interior of the inflation members.
 5. Thecannulation system of claim 4, wherein the cannula is equipped with atleast one lumen formed in the wall thereof to pass fluid from the fluidsource to the interior of the inflation members to selectively inflateand deflate the inflation members.
 6. The cannulation system of claim 1,wherein at least one radially extending member is configured to seal anaperture formed in the atrial septum through which the cannula can bedisposed.
 7. The cannulation system of claim 1, wherein the at least oneradially extending member comprises a first member and a second memberdisposed distally of the first member.
 8. The cannulation system ofclaim 7, further comprising a dilating structure disposed distally ofthe first member.
 9. The cannulation system of claim 8, wherein thedilating structure is separate from and positioned distally of thesecond member.
 10. The cannulation system of claim 8, wherein thecannula is adapted to be moveable relative to the dilating structuresuch that the dilating structure can be positioned before the cannula ispositioned.
 11. The cannulation system of claim 7, wherein the first andsecond members comprises inflation members.
 12. The cannulation systemof claim 7, wherein the first and second members are configured tosandwich the patient's atrial septum tissue therebetween.
 13. Thecannulation system of claim 1, wherein the at least one radiallyextending member comprises a member adapted to be positioned distal ofthe atrial septum to prevent the inlet of the cannula from being pushedproximally out of the left side of the patient's heart.
 14. Thecannulation system of claim 1, wherein the at least one radiallyextending member comprises a member adapted to be positioned proximal ofthe atrial septum to prevent the fluid inlet of the inflow cannula frombeing pushed distally within the left side of the patient's heart. 15.The cannulation system of claim 1, wherein the at least one radiallyextending member comprises a buckling cuff.
 16. The cannulation systemof claim 15, wherein the buckling cuff comprises first and second cuffmembers.
 17. The cannulation system of claim 1, wherein the at least oneradially extending member comprises an expandable member having aproximal end, a distal end, and an elongate portion extendingtherebetween, the expandable member adapted such that the proximal anddistal ends can be drawn toward each other causing the elongate portionextending therebetween to be expanded radially outward from the cannulato form first and second cuff members, the first and second cuff memberbeing sized larger than the size of an aperture formed in the atrialseptum for placement of the inlet on the left side of the heart.
 18. Thecannulation system of claim 1, wherein the at least one radiallyextending member comprises a fabric.
 19. The cannulation system of claim1, wherein the at least one radially extending member is disposedproximally of a dilating structure adapted to facilitate placement ofthe fluid inlet of the inflow cannula on the left side of the heart. 20.The cannulation system of claim 1, further comprising said pump coupledto said inflow cannula and said outflow cannula.
 21. A cannulationsystem for cardiac support comprising: a cannula including a fluid inletsized and configured for placement within the right atrium of a heart,wherein the cannula is equipped with a plurality of members that extendradially relative to the cannula, and wherein the members are configuredto secure an atrial septum therebetween; and wherein said cannula isconfigured to couple to a pumping assembly.
 22. The cannulation systemof claim 21, wherein the members are mechanically expandable by movingportions of said members relative to said cannula.
 23. The cannulationsystem of claim 21, further comprising said pump coupled to saidcannula.
 24. A cannulation system for cardiac support comprising: aninflow cannula including a fluid inlet sized and configured to extendthrough an atrial septum for accessing an atrium or a ventricle of aheart and a lumen extending proximally from the fluid inlet; said inflowcannula being configured to couple to a pump to withdraw blood from theheart through the lumen; an outflow cannula configured to couple to thepump and adapted to extend into fluid communication with the arterialsystem for delivering the withdrawn blood into the arterial system toprovide heart support; and at least one anchor member disposed adjacentthe fluid inlet and configured for securing the cannula system inposition through the atrial septum.
 25. The cannulation system of claim24, further comprising said pump coupled to said inflow cannula and saidoutflow cannula.
 26. A cannulation system for cardiac supportcomprising: an inflow cannula including a fluid inlet and a lumenextending proximally from the fluid inlet, the inflow cannula configuredto extend through a heart wall to place the fluid inlet in fluidcommunication with an atrium or a ventricle of a heart; said inflowcannula configured to couple to a pump to withdraw blood from the heartthrough the lumen; an outflow cannula configured to couple to the pumpand adapted to extend into fluid communication with the arterial systemfor delivering the withdrawn blood into the arterial system to provideheart support; and at least one anchor member disposed adjacent thefluid inlet and configured for securing the cannula system in positionthrough the heart wall.
 27. The cannulation system of claim 26, whereinthe fluid inlet comprises an aperture at the distal end of the cannula.28. The cannulation system of claim 27, wherein the system is configuredsuch that, in use, a length of the cannula extending proximally from thefluid inlet is advanced into the left side of the heart.
 29. Thecannulation system of claim 26, further comprising a dilator configuredfor insertion through the heart wall, a distal portion of the cannulabeing configured to be passed through the dilator into the left side ofthe heart.
 30. The cannulation system of claim 25, further comprisingsaid pump coupled to said inflow cannula and said outflow cannula.
 31. Aheart assist system for coupling into fluid communication with a chamberof a heart comprising: a blood pump including an inlet; an elongate bodyincluding a first end, a second end, and a lumen adapted to be coupledinto fluid communication with said inlet, said lumen extending along alongitudinal axis, said first and second ends defining openings intosaid lumen; a dilating structure disposed about said elongate body andadapted to be positioned proximally of a portion of said second end in adirection toward said first end, and expanding radially outward fromsaid longitudinal axis and in said direction; and a ring member disposedaround said elongate body and said longitudinal axis, said ring memberbeing spaced from said dilating structure and being adapted forretaining said elongate body in a position relative to a wall of thechamber of the heart.
 32. The heart assist system of claim 31, furthercomprising a second elongate body, the dilating structure being disposedon said second elongate body.
 33. The heart assist system of claim 31,wherein said ring member comprises an inflatable balloon.
 34. The heartassist system of claim 33, further comprising a second elongate body,the inflatable balloon being disposed on said second elongate body.